What is the mass of one mole of magnesium nitrate Mg(NO_3)_2?

Jan 2, 2016

Got me! I know that 1 mole of magnesium has a mass of 24.3 g.

Explanation:

And I know that 1 mole of nitrogen has a mass of 14.01 g, and that 1 mole of oxygen has a mass of 15.99 g. Do you think that by adding the masses together, appropriately weighted, i.e. $1 \times M g + 2 \times N + 6 \times O$, you would arrive at the formula mass of $M g {\left(N {O}_{3}\right)}_{2}$?

After you do that, you could see if your summation is right. Good luck.

Jan 2, 2016

It is equal to the molecular weight, 147 grams. Use the mole definition.

Explanation:

Mole is defined as:

$n = \frac{m}{M r}$

where:

$m$ is the mass in grams.
$M r$ is the molecular weight of the substance.

The molecular weight of a substance is equal to the sum of the molecular weights of the atoms that constitute it. For these atoms:

$M g : 24.3$
$N : 14$
$O : 16$

So the molecular weight:

$M g {\left(N {O}_{3}\right)}_{2} = M g {N}_{2} {O}_{6}$
$M r = 23 + 2 \cdot 14 + 6 \cdot 16$
$M r = 147$

Therefore:

$n = \frac{m}{M r}$

$m = n \cdot M r = 1 \cdot 147 = 147 g r a m s$